generalize get_main and get_init to get_method

to get at those know methods that really
__must__ exists, hence the bang, raise if don't
about to add method missing and raise to the list

lib/mom/macro/init.rb

@@ -2,6 +2,8 @@ module Mom
   class Init < Macro
     def to_risc(compiler)
       builder = compiler.builder(compiler.source)
+      main = Parfait.object_space.get_method!(:Space, :main)
+
       builder.build do
         factory! << Parfait.object_space.get_factory_for(:Message)
         message << factory[:next_object]
@@ -9,7 +11,7 @@ module Mom
         factory[:next_object] << next_message
       end
       builder.reset_names
-      Mom::MessageSetup.new(Parfait.object_space.get_main).build_with( builder )
+      Mom::MessageSetup.new(main).build_with( builder )
 
       builder.build do
         message << message[:next_message]
@@ -22,7 +24,7 @@ module Mom
       builder.build do
         ret_tmp << exit_label
         message[:return_address] << ret_tmp
-        add_code Risc.function_call( "__init__ issue call" ,  Parfait.object_space.get_main)
+        add_code Risc.function_call( "__init__ issue call" ,  main)
         add_code exit_label
       end
       compiler.reset_regs

lib/parfait/space.rb

@@ -113,16 +113,15 @@ module Parfait
       methods
     end
 
-    # shortcut to get the main method. main is defined on Space
-    def get_main
-      space = get_class_by_name :Space
-      space.instance_type.get_method :main
-    end
-
-    # shortcut to get the __init__ method, which is defined on Object
-    def get_init
-      object = get_class_by_name :Object
-      object.instance_type.get_method :__init__
+    # shortcut to get at known methods that are used in the compiler
+    # arguments are class and method names
+    # returns method or raises (!)
+    def get_method!( clazz_name , method_name )
+      clazz = get_class_by_name( clazz_name )
+      raise "No such class #{clazz_name}" unless clazz
+      method = clazz.instance_type.get_method(method_name)
+      raise "No such Method #{method_name}, in #{clazz_name}" unless method
+      method
     end
 
     # get the current instance_typ of the class with the given name

lib/risc/builder.rb

@@ -19,6 +19,7 @@ module Risc
     # call build with a block to build
     def initialize(compiler, for_source)
       raise "no compiler" unless compiler
+      raise "no source" unless for_source
       @compiler = compiler
       @source = for_source
       @source_used = false
@@ -207,7 +208,7 @@ module Risc
     def call_get_more
       factory = Parfait.object_space.get_factory_for( :Integer )
       calling = factory.get_type.get_method( :get_more )
-      calling = Parfait.object_space.get_main #until we actually parse Factory
+      calling = Parfait.object_space.get_method!(:Space,:main) #until we actually parse Factory
       raise "no main defined" unless calling
       Mom::MessageSetup.new( calling ).build_with( self )
       self.build do

lib/risc/callable_compiler.rb

@@ -14,6 +14,7 @@ module Risc
     # Must pass the callable (method/block)
     # Also start instuction, usually a label is mandatory
     def initialize( callable  , mom_label)
+      raise "No method" unless callable
       @callable = callable
       @regs = []
       @constants = []